Cycled-concentration distiller

Abstract

A distiller ( ) that employs a rotary heat exchanger ( ) introduces water to be evaporated into evaporation chambers ( ). During most of its operation, it collects the water that has passed through the evaporation chamber ( ) without evaporating, and it reintroduces the thus-collected liquid back into the evaporation chamber, where it also adds a minor amount of unrecirculated feed liquid to make up for evaporation and concentrate removal. Simultaneously, a minor amount of feed liquid is fed into one side of a transfer pump ( ). During this mode of operation, the impurities concentration in the recirculating liquid tends to increase as a result of the evaporation of pure water vapor. Periodically, the erstwhile recirculating liquid is redirected to the other side of the transfer pump ( ), where it causes the feed liquid stored in the transfer pump's first side to be fed without accompanying recirculant liquid into the rotary heat exchanger's evaporation chambers. After a short time, the normal flow is restored, and the liquid from the rotary heat exchanger that had been redirected into the transfer pump's other side is discharged slowly as distiller concentrate. The resultant impurities concentration in the concentrate output can be as much as nearly twice the average impurities concentration experienced by the heat exchanger's evaporation-chamber surfaces.